C230 ACC Troubleshoot

[Sully]

Searched without solution. Looking for direction before I purchase a 24hr. ride at http://www.startekinfo.com/.

Subject: 98 C230 102500 mi

Problem: Hissing/leaking air sound while using ACC. Started abrubtly and can be heard while system is providing warm air/heat.

Details: While ACC is running (in Auto or manual settings), particularly while heating, there is a loud hissing/air leak sound from dash area. May be located on passenger side. The pitch of the sound changes slightly in a cyclical manner. The sound is alleviated by changing the direction of the airflow to ^ only. If airflow is directed v or >v, the noise returns. However, it is no longer cyclical. Heat and AC work well and air appears to be moving through all vents. Airflow seems to correspond with display reading.

Attempted: I changed the filter - it was dirty in there! I checked all visible vacuum lines and was unable to find any that were loose or cracked. I was unable to track down the problem after removing the glovebox and the panel underneath the passenger side dash area. No trouble codes using the high/low temp/REST combo selection.

Suggestions/direction would be appreciated. I have no experience working with ACC, but I am willing to try. I am going to buy a day's worth of startekinfo. If possible, I would like to know where to look first.

Thanks in advance.

PS- The Germans not only make fine automobiles, they brew a fine beer. On tap right now - Franziskaner Hefe-Weisse Dunkel. Mmmmm.

[ronald_m]

Sounds like your low on freon.

[Sully]

at the level. Thanks.

Any idea why low freon would cause noise when system is heating air?

[Sully]

Amazing what an afternoon of driving will get you - codes. All from system after vehicle was not driven for about four hours.

Codes from ACC DTC Memory:

23°3, 41°6, 41°7, 41°9

Used the chart provided by Stevebfl at http://www.continentalimports.com/ser_ic40142.html. Results:

Refrigerant temp sensor - 23°3
Coolant circulation pump - 41°6
Duovalve left - 41°7
Electromagnetic clutch - 41°9

Actual Values:

01 - 66F
02 - 57F
03 - 103
05 - 40
06 - 89F
07 - 10°0 dropped into the 9's while reading
08 - 95F
09 - 41F
10 - 20 5
20 - 00
21 - 070
22 - 000
23 - 000
24 - 13.8
40 - 02
41 - 03
42 - 18
43 - 6-C
50 - 96F
51 - HI
52 - 50F
54 - Off

Any input would be appreciated. Looks like I am going to need more beer.

[ronald_m]

The values looks good.Probably you have a vent leak.

[Sully]

Actual values 3 and 5 showed same temp. After reading several posts about evap temp sensors, I thought/hoped it was the culprit. However, it does not appear so. The sensor temp never showed higher than 40F, even during operation. The only suspect value, in my completely uninformed view, was #7. It never rose higher than 8. However, I am sure the AC was not working too hard as it is only 50F here. The hissing/leak sound persisted while the ACC brought the temperature up to 72 and then stopped while the system appeared to be using outside/cool air to maintain the selected temp.

I deleted the codes from the DTC Memory. After running the morning errands, code 41°9 returned. I should mention that the DTC seems to have two menus. The first dlA switches immediately to END. The second dl°A showed all the codes listed yesterday and the code from this morning. A fan icon is also displayed in the dl°A menu. I did not clear the code this morning.

I am not sure if the above is of any value when diagnosing. I am going to buy into the tek website after I have a better idea of what is going on.

Thank you for the help.